The present invention relates to an automatic transmission which may be installed to automotive vehicles, and in particular, relates to a lubrication structure of its transmission mechanism.
For such an automatic transmission, which achieves a multi-gear shift with selection of power transmission paths of the transmission mechanism, to which an engine output rotation is inputted via a torque converter, by selectively connecting plural frictional elements, it may be a problem how to supply lubricating oil to the rotational elements which constitute the transmission mechanism in order to improve functions, durability and the like.
In an automatic transmission which is described in Japanese Patent Laid-Open Publication No. 2006-214580, for example, for lubrication of a bearing portion of a pinion of a planetary gear set, lubricating oil which flows out of an oil hole, which is formed so as to extend in a radial direction from an oil passage which is formed at a center axis portion so as to extend in an axis direction, due to a centrifugal force is supplied into an oil passage which is formed in a carrier body of the planetary gear set, and then the lubricating oil is supplied to the lubrication portion between the pinion and a pinion shaft via an oil passage which is formed in the pinion shaft so as to extend in an axis direction and an oil hole which is formed so as to extend from the oil passage and reach an outer peripheral face of the pinion shaft.
According to the above-described automatic transmission, however, the lubricating oil having flowed out of the oil hole is discharged into a space in a transmission case, and then part of the lubricating oil is supplied into the oil passage of the carrier body, so that the lubricating oil may be supplied to not only the bearing portion of the pinion but other portions. Therefore, the supply amount of lubricating oil to the bearing portion of the pinion may change in accordance with respective rotational states of the rotational elements of the planetary gear set which include the above-described center axis portion and the like. As a result, there occurs a problem in that in case the pinion rotates at a high speed, the sufficient amount of lubricating oil would not be supplied to the bearing portion of the pinion, resulting in a poor wear resistance for the pinion and the pinion shaft.